It is well known that electrostatic discharges (ESD) can damage electronic devices. Examples of such sensitive devices are semiconductor wafers, magnetic heads for disk drives, integrated circuits, other electronic components and circuits, etc. The ESD can disrupt operation of an electronic circuit as well. In non-electronic applications such as powder handling, etc., ESD can be a cause of fire.
Short transient spike-like signals resulting from ESD events, commutation of electric motors, solenoids, etc. and from other sources can also induce damage to electronics devices and cause circuit malfunction. Also, improperly done ground wires can be a media for transmitting surges as well.
Presently, the most common method of reducing damages caused by ESD is preventive: grounding wrist-wraps, conductive chairs, conductive floor coating, ionizers, etc. All these measures are supposed to reduce or eliminate build-up of static voltage that causes discharges. However, the ultimate indication of the effectiveness of ESD-preventive measures is actual occurrence of electrostatic discharge (ESD) events known as ESD Events. The detection, measurement of magnitude of the ESD Events and data logging the data for future analysis presents valuable information for assessment of the ESD environment, ESD protection, real-time addressing of the ESD problems, determining most likely defects due to ESD, and statistical process analysis.
The ESD Event detection devices available today, such as that shown in U.S. Pat. No. 4,631,473 to Sanki and Lucent' T100 provide an indication of ESD events that exceeded a preset level. However these devices merely detect that ESD Events have occurred without the ability to measure the magnitude of the ESD Events. The knowledge of the magnitude of ESD events provides valuable information pertinent to assessment of potential damage caused by ESD and also effectiveness of ESD-preventive measures. In addition, existing devices are geared towards occasional ESD checks, rather than day-to-day ESD monitoring. The continuous ESD monitoring would offer a real-time indication of ESD problems and provide immediate feedback for implementation of ESD-corrective and preventive measures.
ESD events last for a very short period of time (typically, nanoseconds). This makes it very difficult to provide a measurement of the magnitude of these ESD events in a practical cost-effective and user-friendly manner. Often, a high-speed oscilloscope and an antenna are used to capture the waveform of an ESD Event for analysis of its magnitude. This technique is not practical for everyday use. Thus, it is desirable to provide a device that is able to detect ESD events, the magnitude of the ESD events and distinguish actual ESD events from other transient signals. Thus, it is desirable to provide an ESD event and transient signal detection and measurement device and method and it is to this end that the present invention is directed.